A network may be provided enabling communication entities to communicate with each other. The communication entities may be wireline telephones, mobile telephones or any other suitable device. The communication entities that initiate communication may be referred to as calling entities and the communication entities with which the calling parties initiate communication are referred to as remote entities or called entities.
In the telecommunications network a call initiated by a calling entity and destined for a remote entity is routed through a number of switching nodes before this call reaches its destination. An example of how a call may be routed from a calling entity to a remote entity in a telecommunications network is given with reference to FIG. 1. A calling entity CE-A sets up a call to a called entity CE-B by sending a call set up request message to a switching node 101. The switching node 101 receives the call set up request message and analyses the destination number comprised therein, i.e. typically a number associated to called entity CE-B. Depending on the outcome of the analysis the switching node 101 will select the most appropriate next switching node for routing the call further in the most efficient way. In this example the switching node 101 selects a switching node 102. Switching nodes 102 and 103 behave in a similar way and route the call further towards switching node 104, which is closest to the called entity CE-B. Switching nodes 102 and 103 are sometimes also referred to as transit switching nodes, because they function as transits between switching nodes 101 and 104. The switching node 104 then connects the incoming call to called entity CE-B and a speech connection may be opened between calling entity CE-A and called entity CE-B.
According to the Intelligent Network (IN) concept, service intelligence or service logic is separated from switching functions. This separation enables network operators to develop and deploy services and features independently of network vendors, allowing more flexibility in service development, simplified rollout, reduced cost and greater autonomy. Examples of IN protocols are the Intelligent Network Application Protocol (INAP), the Advanced IN (AIN), and the Customized Applications for Mobile network Enhanced Logic (CAMEL). INAP was developed for fixed line networks and is the primary protocol used for fixed line IN outside of North America. AIN is a variant developed for North America.
CAMEL
CAMEL is a Global System for Mobile communications (GSM) Phase 2+ and Wideband Code Division Multiple Access (WCDMA) network feature specified in 3GPP TS 22.078. CAMEL is based on core INAP with modifications to take into account, amongst others, subscriber mobility. In particular, CAMEL enables the use of operator-specific services by a subscriber even when roaming outside the subscriber's Home Public Land Mobile Network (PLMN). A CAMEL-based Intelligent Network comprises as main entities a service switching entity for switching tasks, also referred to as SSF (Service Switching Function) or gsmSSF (GSM Service Switching Function) and a service control entity comprising the service intelligence or logic also referred to as SCF (Service Control Function) or gsmSCF (GSM Service Control Function).
FIG. 2 depicts a schematic overview of a telecommunications network comprising an intelligent network.
The intelligent network comprises a service control entity SCE and a service switching entity SSE, which will both be explained in more detail below. Furthermore, switching nodes 203, 204 and 205 are depicted, each of which may be a Mobile Services Switching Centre (MSC). The switching node 203 may function as an originating node; the switching node 204 may be a transit switching node and the switching node 205 may be a terminating node.
Intelligent networks services are executed at the service control entity SCE. The service control entity SCE is able to communicate with the service switching entity SSE using an intelligent network protocol such as CAMEL or INAP. The service switching entity SSE, when controlling the call from calling entity CE-A to called entity CE-B, is preferably co-located with switching node 203, but may also be co-located at another switching node.
The service control entity SCE has a leading role in the intelligent network and may decide that some services are allowed or disallowed for a call. It sends instructions to the service switching entity SSE to be carried out by the service switching entity SSE.
With the application of the intelligent network concept, there are effectively two levels of call control: (1) call control by the switching node and (2) call control by the SCE. Because of the two levels of control that are also separate from each other, inconsistencies may occur when an IN service is invoked for a call that may be in addition subject to a service executed at a switching node. This may be, for example, the case when a first communication entity CE-A sets up a multi party call. Prior to the establishment of the multi party call, the first communication entity CE-A may be involved in two calls, a first call with a second communication entity CE-B which is active and on hold, and a second call with a third communication entity CE-C (explained below with reference to FIG. 6) which is active and in speech connection. The first communication entity CE-A may then initiate a multi party call in which the two calls are merged (explained below with reference to FIG. 7).
Multi Party Service
Multi party service is a so-called supplementary service or network based service that is executed by and under the control of switching nodes, such as MSCs. The multi party service provides a first communication entity CE-A (calling or called entity) with the ability to establish a multi-connection call, i.e. a simultaneous communication with a second and third communication entities. In fact, also more then three communication entities may be involved. The communication entity having established a multi party call may be referred to as “multi party served subscriber” or “multi party served entity”. It be emphasised that when an entity establishes a multi party call, the respective calls that are connected to or from this call entity may, independently of each other, be incoming or outgoing. The communication entities that participate in the multi party call but did not initiate the multi party call are also referred to as remote communication entities.
For the GSM and the 3G network, the Multi party service is specified in 3GPP technical specification 22.084.
For example, the multi party served entity CE-A is involved in two calls; one active call in speech connection with second communication entity CE-B and one active call on hold with third communication entity CE-C, both calls having been answered by the respective called second and third communication entity CE-B, CE-C respectively. In this situation the multi party served subscriber CE-A may request the network to execute the multi party service.
Once a multi party call is established, additional communication entities may be added to the multi party call, disconnected from the multi party call, temporarily separated (i.e. removed) from the multi party call and, when temporarily separated, reconnected to the multi party call.
Subscribers or communication entities participating to a multi party call may be referred to as conferee.
An acknowledgement is sent towards the multi party served subscriber CE-A at the invocation of this supplementary service while a notification is sent towards all the remote parties in a multi party call. The multi party call will, just after it has been established, be constituted just by three parties, that is the multi party served subscriber (first communication entity CE-A) and the other two subscribers (second and third communication entity CE-B and CE-C) that till the moment of invocation were engaged in two separated calls with the multi party served subscriber (first communication entity CE-A). At this stage other communication entities (fourth, fifth etc.) can be included in the multi party call if the multi party served subscriber decides hereto. A notification may be sent towards all remote communication entities, i.e. second, third etc. communication entities (i.e. not towards the multi party served subscriber CE-A) every time a new communication entity is added to the multi party call. Notifications may also be sent to remote communication entities when they are put on hold and when they are retrieved; these notifications related to hold and retrieve are in accordance with normal Call Hold procedures.
The multi party service as stated before, is a network based service that is executed by and under control of switching nodes, whereas IN services are executed under the control of a service control entity and invoked for certain calls only. Because of the two levels of control that are also separate from each other, inconsistencies may occur when an IN service is invoked for a call that may be in addition subject to a multi party service executed at a switching node.
It is an object to provide a solution to improve the handling of a multi party call in a telecommunications network.